Sonja Kovalevsky, actually Sofja Kovalevskaya, (1850–1891) was a Russian mathematician and writer.
She wrote works in the theory of abelian functions, as well as in the theory of partial differential equations, where she provided conditions for the existence of analytical solutions (Cauchy–Kowalevski theorem).
In 1881, Sonja Kovalevsky moved to Sweden, and in 1884 she became an associate professor at Stockholm University. She went on to be appointed professor in 1889, thus becoming Sweden's first female professor and the world's second female mathematics professor.
Sonja Kovalevsky also wrote several fictional novels, such as the autobiographical novel A Russian Childhood (1889), and the drama Kampen för lyckan,"The Fight for Happiness" (1887), which she co-wrote with Anne Charlotte Leffler.